Politics: Perhaps Democrats know something the rest of us don't about Barack Obama's political fortunes. What else explains the increasing numbers who are openly defying the president on two key election issues?

The notoriously thin-skinned Obama could not have been happy with the news last week that, as the Hill newspaper put it, "an increasing number of Democrats are taking potshots at President Obama's health care law."

North Carolina's Brad Miller, who voted for the law, now laments that "we would all have been better off" if Congress had dealt with more pressing issues "and then came back to health care."

Barney Frank complained that the Democrats "paid a terrible price for health care." And Virginia's outgoing Sen. Jim Webb said the law would be Obama's "biggest downside" in the election and had cost him "a lot of credibility as a leader."

Meanwhile, stalwart Massachusetts liberal Elizabeth Warren is now calling to repeal a piece of ObamaCare — the 2.3% tax on medical devices — because, she says, it "disproportionately impacts the small companies with the narrowest financial margins."

Warren, by the way, is running for the Senate seat occupied by Republican Scott Brown, whose victory in 2010 was a result of the public's intense opposition to ObamaCare.

Former Alabama Rep. Artur Davis went furthest. "I think the Affordable Care Act is the single least popular piece of major domestic legislation in the last 70 years," he said. "It was not popular when it passed; it's less popular now." Ouch.

These Democrats are no doubt familiar with polls that show surprisingly little support for ObamaCare within their ranks. Fewer than half of Democrats think the government should be able to force individuals to buy insurance — the core element of ObamaCare — according to the latest IBD/TIPP poll. Only a little more than a third say the Supreme Court should "uphold the entire law."

The fact that they're willing to trash-talk Obama's single biggest legislative achievement suggests they're worried about something more than how the Supreme Court will rule.

This fear is even more evident when you look at the growing opposition among Democrats to Obama's position on the Keystone XL pipeline.

Obama may have thought he'd cleverly handled the issue by putting it off until next year, and that no one would think to defy his veto threats.

But when Republicans called his bluff with a bill to force a start on construction, 69 Democrats rushed to join them, giving the House bill a veto-proof majority. The Senate bill is just a vote or two away from overcoming a Democratic filibuster.

The importance of this fight is huge. If Democrats defy him, it will severely undermine Obama's claim that he's pursuing an all-of-the-above energy strategy.

Obama came to the White House claiming that he alone was qualified to unite the country behind common objectives. The fact that he's losing support from his own party on two of the most important issues of the day is significant.